Wet fixation of modifying agents on fibrous systems by heating in aqueous salt solution

ABSTRACT

MODIFYING AGENTS SUCH AS CREASEPROOFING PRECONDENSATES OR DYES, ARE WET FIXED IN A WATER-SWELLABLE FIBROUS SYSTEM OR WEB SUCH AS A CELLULOSE-CONTAINING FABRIC BY APPLYING AN AQUEOUS SOLUTION CONTAINING ONE OR MORE SUCH AGENTS OF THE DESIRED TYPE TO THE WEB AND THEREAFTER FIXING SUCH AGENTS IN THE WET WEB BY IMMERSING IT IN A HOT AQUEOUS SALT SOLUTION WHICH CONTAINS ONE OR MORE STABLE SALT OF A STRONG ACID WHICH DOES NOT DECOMPOSE IN WATER SUCH AS SODIUM SULFATE. THIS WET FIXATION TECHNIQUE IS USEFUL IN IMPARTING DIMENSIONAL STABILITY TO CELLULOSIC WEB SUCH AS COTTON FABRICS OR PAPER OR IN OTHERWISE MODIFYING THEIR PHYSICAL OR CHEMICAL PROPERTIES E.G., IN DYEIBG THEM. THE SALT SOLUTION SERVES TO PREVENT OR MINIMIZE MIGRATION OF THE TREATING AGENT FROM THE FIBERS DURING A FINISHING OPERATION.

3,709,716 WET FIXATION OF MODIFYING AGENTS ON FIBROUS SYSTEMS BY HEATING IN AQUE- GUS SALT SOLUTION Robert W. Liggett, Mountain Brook, Ala., assignor to Cotton Producers Institute, Memphis, Tenn. No Drawing. Filed June 17, 1969, Ser. No. 834,171 Int. Cl. D06m 15/54 US. Cl. 117-63 9 Claims ABSTRACT OF THE DISCLOSURE Modifying agents such as creaseproofing precondensates or dyes, are wet fixed in a water-swellable fibrous system or web such as a cellulose-containing fabric by applying an aqueous solution containing one or more such agents of the desired type to the web and thereafter fixing such agents in the wet web by immersing it in a hot aqueous salt solution which contains a water soluble stable salt of a strong acid which does not decompose in Water, such as sodium sulfate. This wet fixation technique is useful in imparting dimensional stability to cellulosic webs such as cotton fabrics or paper, or in otherwise modifying their physical or chemical properties, e.g., in dyeing them. The salt solution serves to prevent or minimize migration of the treating agent from the fibers during a finishing operation.

BACKGROUND OF INVENTION Considerable work has been done in recent years on improvements in processes for imparting durable press properties to fibrous systems in general, and cellulose or cotton-containing fabrics in particular. A particularly promising approach has involved the Wet fixation of resinforming creaseproofing agents such as formaldehydemelamine precondensates, as disclosed, for instance, in US. Pat. 3,138,802 to Getchell. In this type of process a fiber system such as a cotton fabric is presensitized for durable press processing by fixation of a suitable resin former or creaseproofing agent within the fibers while they are wet and swollen but without greatly altering the dry crease recovery angle or durable press properties of the fiber system. The latter properties are only imparted during a subsequent dry cure.

Such a process accordingly permits ready creasing or other distinct shaping of the fiber system during apparel manufacture or the like subsequent to the wet fixation step and prior to the delayed dry cure, However, wet fixation offers a better balance of product properties even when the dry cure precedes the garment manufacture or final product shaping.

Especially promising results have recently been obtained by conducting such wet fixation in a steam atmosphere which tends to cause particularly rapid and extensive swelling of cellulosic fibers and thereby facilitates even penetration of creaseproofing agents into the fibers. This leads to economies in processing time as well as the amount of the creaseproofing agent consumed in the process. However, wet fixation in a steam atmosphere requires special steaming equipment which many finishers do not posses. Moreover, such fixation processes employing steam are somewhat diflicult to conduct in a controlled, consistently reproducible manner, because the prevalent creaseproofing agents of the formaldehydemelamine or formaldehyde-urea precondensate type tend to hydrolyze and lose formaldehyde when the fiber system is exposed to the steam atmosphere for more than a minute or two. At times, problems can also arise due to the undesirable deposition and curing of resin forming agents United States Patent ice on the rollers or other surfaces over which the sensitized fabric is transported in the steam chamber.

Accordingly, it is an object of this invention to provide a wet fixation process that does not require any special steaming equipment but permits ready processing at high speed as well as efiicient utilization of modifying agents of all kinds, including, for instance, creaseproofing agents or dyes. Another object is to provide a wet fixation process which can be safely conducted at or near steam temperature, without excessive loss of volatile or soluble components from the fiber-modifier system, without undesirable condensation of steam upon the fabric and with minimum deposition of treating agent or resin on the treating equipment. Another and more particular object is to provide a continuous wet fixation process for the ultimate imparting of durable press properties to cellulosic fabrics, which process can be conducted at high rates and at a temperature which may be near C. or higher without an undue loss of formaldehyde or other volatiles and with good and readily reproducible end results.

SUMMARY OF INVENTION A wet fixation process has now been developed which does not require open steaming but nevertheless is capable of being operated at production rates and treating agent efficiencies comparable to those obtained in open steam wet fixation, and, especially in the case of durable press fabrics, gives good fabric performance while lending itself to convenient operation and effective control.

More particularly, it has now been discovered that good wet fixation can be obtained by immersing a waterswellable fiber system or fabric, after an appropriate pick-up of aqueous solution of modifying agent has been applied thereto, in an aqueous bath of a salt which is stable in solution at the pH and temperature used in the wet fixation step such that the bath limits or reduces the migration of the previously applied agent out of the fabric into the bath without having any other objectionable effect on the fabric that is treated. If this treatment is carried out at super-atmospheric pressure, treating temperatures higher than the atmospheric boiling points of the process liquids may be employed, though operation at or near atmospheric pressure is usually most convenient and consequently preferred, Upon removal from the bath the fabric is promptly cooled and/or neutralized to substantially arrest any continued polymerization of the creaseproofing agent or precondensate within the fabric or loss of volatile products (e.g., formaldehyde) from the fabric. Residual bath liquid is then removed from the fabric by any suitable procedure, such as by mangling and washing in water. If the fabric at this stage shows substantial acidity it may be advantageous to neutralize it before drying in preparation for use in subsequent stages of durable press processing.

The fibers that swell in water and are therefore potentially amendable to treatment in accordance with this invention include silk, wool, poly(vinyl alcohol), and many nylons or polyamides, in addition to natural cellulose polymers such as cotton or regenerated cellulose such as rayon.

If, as a result of neutralization and/or washing subsequent to the wet fixation step, the fabric does not contain adequate curing catalysts, the wet-fixed fabric may be reimpregnated with a solution of an appropriate latent curing catalystsuch as zinc nitrate or magnesium chloride, then dried at a temperature too low to cause curing, as is otherwise well known. The catalyzed fabric containing the creaseproofing agent wet fixed therein may then be processed in other wise conventional manner including dry curing at elevated temperature, e.g., C.

either before or after manufacture of the desired articles therefrom.

DESCRIPTION OF PREFERRED EMBODIMENTS As applied to druable press fabric treatment, the practice of the present invention characteristically involves the use of a creaseproofing agent or a combination of creaseproofing agents which, on the one hand, will polymerize inside the cotton fiber while it is wet and swollen, so that the polymeric material so formed is fixed within the fibers, and on the other hand will subsequently crosslink the cellulose when cured in the dry state under suitable conditions in the presence of an appropriate catalyst.

The preferred polymer-forming creaseproofing agents at this time include the melamine-formaldehyde and the phenolformaldehyde precondensates, though other N- methylol containing, polymer forming compounds such as urea-formaldehyde precondensates are also useful,

Bifunctional cross-linking agents, such as dihydroxydimethylolethyleneurea or the closely related methylolated propylene urea derivatives may be added to ensure adequate performance of the treated fabric. If the polymer former itself is highly methylolated and consequently can furnish sufiicient formaldehyde for adequate cross-linking in the final dry cure, the inclusion of a separate crosslinking agent is not required.

Polymer formers The polymer formers useful herein include particularly the easily hardenable precondensates which are substantially water soluble and are obtained by condensation of formaldehyde with a compound such as melamine or a lower alkyl substituted melamine, a urea, or a phenol such as resorcinol. The resulting methylol containing compound or precondensate may further be etherified by reaction with a lower alkanol such as methanol or butanol. As is well known in the fabric treating art, these precondensates are capable of being applied to the cellulosic material from an aqueous solution and to be readily wet fixed or insolubilized therein as described, for instance, by Getchell in US. Pat. 3,138,802. Triazines obtained by condensing a lower alkyl substituted melamine and formaldehyde are examples of such precondensates.

Good results are obtained, for instance, using precondensates obtained by condensing 1 mole of melamine or an alkyl substituted melamine with 2 to 6 moles of formaldehyde, i.e., using di-, tri-, tetra-, penta-, or hexamethylol melamine. Precondensates having formaldehyde/melamine ratios of at least 4:1 are usually preferred. Such products function well as polymer formers which can be readily wet fixed in the material by steaming as described herein. Subsequently, under high temperature curing conditions, they are capable of acting as formaldehyde donors, with the result that the liberated formaldehyde functions as a cross-linker, imparting the desired durable press characteristics to the cured material.

Commercially available products of this kind include Aerotex 23, an alkylated melamine-formaldehyde precondensate; Aerotex M-3, a dimethoxymethylhydroxymethylmelamine; Aerotex P-225, hexakis (methoxymethyl) melamine; and Aerotex 19, which is a less completely fractionated modification of Aerotex P225. These products are supplied in the form of aqueous solutions by American Cyanamid Company.

Cross-linkers An important characteristic of the creaseproofing agent or a component thereof is that it should be capable of cross-linking cellulose after the wet fixation stage under normal dry curing conditions and in the presence of a suitable catalyst.

If the polymer former is highly methylolated (e.g., a precondensate obtained by condensing one mole of melamine or an alkyl substituted melamine with 4-6 moles of formaldehyde), sufficient formaldehyde may remain fixed within the polymeric material deposited in the cotton to ensure adequate cross-linking in the subsequent high temperature cure, either by cross-linking through the polymer itself, or by liberation of formaldehyde which can then act as a cross-linker in its own right.

In cases where a single precondensate is insufiiciently effective as both polymer former and cross-linker, however, it is necessary to use a combination of agents at least one of which is predominantly a polymer former while another is primarily a cross-linker. Bifunctional cross-linking agents do not readily form polymers within the fiber, and thus do not, alone, confer the advantages associated with wet fixation. However, when used in conjunction with a polymer former under suitable conditions, the cross-linking potential of the wet-fixed fabric may be raised by the presence of the cross-linking agent, with a consequent improvement in the smoothness and wrinkle recovery of the fully treated fabric.

Suitable cross-linking agents include the highly reactive condensates of formaldehyde and a S-membered cyclic ethylene urea of the kind shown in US. Patent 3,177,093. Especially useful are products such as dihydroxydimethylolethyleneurea, DHDMEU, available as Permafresh 183 or, in a somewhat modified and less reactive form, as Permafresh 113B, from Sun Chemical Company. The similar modified propylene urea compounds such as Fixapret PCL, available from Badische Anilin and Sodafalbriken are similarly useful. Condensates having on the average at least one and one-half moles of formaldehyde combined as methylol groups with a cyclic urea are suitable and the dimethylol derivatives are preferred. However, it is similarly feasible to use other known crosslinking agents such as the rapidly acting triazones, N- methylol carbamates, or aldehydes themselves such as formaldehyde, glutaraldehyde and glyoxal. Still other cross-linking agents include tris(l-aziridinyl)phosphine oxide, divinyl sulfone, epoxy resins, etc. In fact any compound which will act to form cross-links between adjacent cellulose molecules or between the cellulose and the polymer deposited within the fiberstructures may be used here.

Dyes

Dyes which may be wet fixed in cellulose webs in acoordance with this invention are essentially those that may be applied by conventional aqueous methods, such as direct cotton dyes, sulfur dyes, vat dyes, reactive dyes, and particularly acid dyes and other wool type dyes if a N-methyllol polymer is also present in the web. Alkaline reacting baths may be preferred for application of sulfur and vat dyes while neutral salts may be preferred for direct dyes.

Specific examples of such dyes include Sky Blue 6BX (Cl. Direct Blue 1), Brilliant Orange RK (CI. Vat Orange 3), Brilliant Yellow M-6GS (C.I. Reactive Yellow), and Sulfur Black 2B (C.I. Sulfur Black 1). Other well-known dyes are similarly usable and may be chosen from among those listed in the Color Index or from the AATCC Handbook.

For applying these dyes by the conventional aqueous methods, a suitable dilute solution or dispersion of the dye with auxiliary agents is first prepared, and fabric is then immersed in the dye bath for a sufficient time (20 minutes to 1 hour) and at a high enough temperature (up to the boiling point of the liquid) to insure uniform diifusion of the dye through the fibers and exhaustion of the dye onto the fabric. Unlike these conventional procedures, wet fixation of dyes in an aqueous salt bath may be carried out in accordance with the present invention by first padding the fabric with the desired formulation and then immersing the padded fabric for from about 15 seconds to about 5 minutes, preferably about 30 to seconds, in the heated salt solution. By this procedure,

uniform dyeings can be achieved in as little as one minute at 100 C.

Other treatments The wet fixation process employing aqueous salt baths may also be used in still other types of fiber or fabric treatment, e.g., in the application of flame retardants, mildew inhibitors, etc. For instance, it may be applied to flame-retardant finishing with reactive phosphorus compounds, such as tris(l-aziridinyl)phosphine oxide, mixtures of phosphorus compounds and nitrogenous resins, such as tetrakis(hydroxymethyl)phosphonium chloride and methylolated melamines, and inorganic salts, such as stannous phosphate. The last may be insolwbilized in the fibers when, for example, the fiber contains stannous chloride and the bath contains diammonium phosphate that react to form the insoluble salt.

Moreover, the present technique offers certain advantages even in certain treatments of materials that do not swell appreciably in water. For instance, in the case of treating olefin polymer fibers such as polypropylene in a blend with cotton salt baths of the type disclosed herein may be used to prevent dye dispersions and organic fiber swelling agents applied during previous padding from migrating too rapidly out of the fabric during subsequent fixation or other treatment.

The present salt bath technique may also be beneficial in processes that are carried out at room temperature. For instance, fabrics may be impregnated with a mixture of acrylate monomer and a ferrous salt (e.g., methyl acrylate or methacrylate and ferrous sulfate or chloride), and then passed through a salt solution at room temperature that contains one or more peroxides (e.g., potassium persulfate in solution and benzoyl peroxide in suspension) to effect polymerization.

The salt bath technique also may be beneficial in wet fixing certain resins under alkaline conditions, i.e., at a pH above 7, and may allow the use of two different cata'lysts for use at different stages, such as one for wet fixation and the other for curing. For instance, one such catalyst may be basic and the other acidic, or one may be highly active for polymerization and the other less active for delayed curing at a higher temperature.

GENERAL PROCEDURE In sensitizing a fiber system for the imparting of durable press properties, a polymer former is used in the form of an aqueous solution which may contain from about to about 25%, preferably 7 to 15%, of the resinous precondensate. To assure rapid wet fixation of such a precondensate in the fabric in the desired amount it is necessary to adjust the pH of the padding solution to a value between 1 and about 4, preferably about 2 to 3, by addition of a strong acid. Hydrochloric or sulfuric acids are preferred but other strong acids such as phosphoric acid, formic acid, acetic anhydride or maleic anhydride, or mixtures of the foregoing may be used similarly.

Unless the polymer former used is also capable of serving, directly or indirectly, as a cross-linker in the final high temperature cure, an active cross-linking agent is preferably included in the same padding bath as the polymer former to provide a concentration of cross-linker in the bath of also between about 5 to 25%.

Instead of including the cross-linker in the same bath as the polymer former prior to wet fixation, it is also possible to apply the cross-linker after the polymer former has been wet fixed in the material, e.g., simultaneously with a latent catalyst such as zinc nitrate or magnesium chloride which is used 00 catalyze the final dry cure.

In addition to the aforementioned resins, the initial padding bath or the latent catalyst bath applied subsequent to wet fixation, or both these baths, may include other agents conventionally used in the art. For instance, softeners such as polyethylene in finely dispersed form,

surfactants, fiame retardants, soil release agents, hand modifiers, water and stain repellents, and so forth, may be included as is otherwise well known.

Application of the resin solution to the cellulosic material can be done by conventional padding using customary equipment, or by spraying and other processes well known in the art. Baths containing about 20% of polymer former are particularly advantageous in the practice of the present invention. Typically, they are applied to the fabric at a wet pick-up of between about 50 to so as to give upon wet fixation a total resin add-on of between about 5 and 15%, preferably between 7 and 12%, based on dry fabric weight. The padding may be conducted at ambient temperature, e.g., between 10 and 30 C.

The wet fixation bath After being thus impregnated with the aqueous solution of creaseproofing agent the fabric is immersed in the aqueous fixation bath which constitutes the central feature of this invention. This fixation bath is heated to below the boiling point of the aqueous mixture previously applied to the fabric. For instance, the fixation bath may have a temperature between about 70 and 130 C., preferably between about and 120 C.

The pH of such a fixation bath is preferably adjusted to be substantially the same as the pH of the active solution with which the fabric was previously impregnated or to produce in the fabric after immersion a pH which is particularly advantageous to accomplish the desired effect. For instance, in wet fixing one of the typical creaseproofing aminoplasts, the pH of the fixation bath may be maintained at a value between about 1 and about 7. In many cases, a pH between about 2 and 4 gives particularly good results.

To be useful herein, the aqueous fixation bath must contain a sufiicient concentraton of a salt or mixed saltand-acid solute such that loss of creaseproofing agent or other active agent from the web being treated is kept at a minimum. In addition, the solute must be one which is stable in solution at the values of pH and temperature desired in the fixation step and which has no marked detrimental effect on the fabric or web under the conditions of use.

Generally speaking, undesirable migration of active agent from the web is avoided when a solution that is saturated at the temperature of use is employed as the fixation bath. However, concentrated solutions that are weaker than saturated under the conditions of use can be employed as the fixation bath without causing undue loss of active agent from the web. In some instances the use of such less-than-saturated solutions may be preferred in that this tends to avoid the formation of solid deposits or precipitates that otherwise may occur in cooler portions of the process where the bath liquid may have been cooled to below its saturation temperature.

Typically, the concentration of solute in the fixation bath may range between about 15% and 75%, preferably between about 20% and 30%. Still more preferably, it is desired to use a solute concentration within this range which is equal to between 50 and of the value which gives a saturated solution at the conditions of use.

For reasons of convenience and economy, aqueous solutions of sodium sulfate, Na SO have been preferred in the work to date. The solubility of this salt in water is about 33% by weight at 40 C. and about 30% by weight at 100 C. Solutions containing 30% Na SO have been found eminently satisfactory under all conditions used.

However, there is nothing particularly critical about the solute used provided that it generally satisfies the conditions outlined above. Accordingly, instead of using sodium sulfate one may use any other sufficiently soluble sulfate of an alkali or an alkaline earth metal, magnesi- 7 um, zinc, aluminum, their various mixed sulfates or alums, their thiocyanates, and so forth; or any of the corresponding chlorides, phosphates, acetates, and other salts that do not decompose and are sufficiently soluble in water and have no deleterious effect on the fabric.

When an acid fixation bath is not required, the corresponding carbonates may also be used. Among these, the use of an ammonium carbonate solution as the fixation bath offers the further advantage of permitting a fabric or web which has been wet fixed in such a bath to be directly dried without any intermediate washing. As ammonium carbonate decomposes at 58 C., it can be removed from the wet fixed fabric simply by drying above this temperature, e.g., between 60 and 80 C.

Salts of the lower alkylamines or the lower alkanolamines, e.g., ethylamine hydrochloride or ethanolamine sulfate, are also operable but in some cases may cause odor problems. For this reason, they are not recommended for use where freedom from odor is an important product requirement.

When it is particularly desired to insure that a fixation bath be used which is saturated with solute under conditions of use, an excess of the solid solute may be included in the fixation tank.

The choice of a particular salt can be used to govern the fiber swelling to a greater or lesser extent. For instance, zinc salts generally tend to promote the swelling effect of water on cellulosic fibers while thiocyantes tend to promote the swelling effect of water on nylons (polyamides) and on acrylics (e.g., acrylonitrile polymers and copolymers) as well as cellulosics.

The dwell time of the impregnated fabric in the hot aqueous fixation bath may vary from as little as about 15 seconds to minutes or more, depending somewhat upon the reactivity of the creaseproofing composition and the severity of the fixation conditions. For instance, high acidity and high bath temperature are factors which permit or make advisable the use of relatively short dwell times whereas low acidity and mild bath temperature make it possible to use long dwell times. As an example, when using an aqueous padding solution containing a highly methylated hexamethylol melamine resin at a pH of about 2 and a fixation bath also adjusted to a pH of about 2 and heated to a temperature of about 98 C., a dwell time in the range of from seconds to 3 minutes gives satisfactory results. Of course, optimum conditions can be readily determined in each case by a few preliminary screening tests.

After removal from the hot fixation bath it is desirable to cool the wet-fixed or presensitized fabric quickly, e.g., by contact with or introduction into cold water. Preferably, the presensitized fabric is consecutively washed in pure water, neutralized in a dilute aqueous solution of an alkaline substance such as a 2% solution of sodium carbonate, washed in water to which a small amount of any conventional detergent may be added, and finally rinsed with water and dried under mild conditions, e.g., at 80 C.

If the creaseproofing agent is wet-fixed in this fabric at an only mildly acidic pH such as between 3.5 and 5, neutralization may be omitted. Indeed, if wet fixation in such a case does not result in making the creaseproofing agent substantially completely water insoluble, any contact between the presensitized fabric and water or aqueous solvent solutions should be avoided until after the creaseproofing agent has been properly insolubilized in the final cure.

When reference is made herein to an operation being conducted under mild drying conditions or with the avoidance of effective creaseproofing, this is intended to mean that such an operation is conducted under conditions which do not alter the dry crease recovery angle of the fibers system to such an extent as to impede the creasing or other distinct shaping of such a fiber system or fabric during subsequent apparel manufacture or the like.

In reimpregnating a wet-fixed fabric with a latent curing catalyst, zinc nitrate, Zn(NO -6H 0, was the most common catalyst used in the work described herein. However, any other appropriate curing catalyst of the type known in the art for this purpose, such as magnesium chloride, ammonium chloride, zinc chloride, etc. may be used similarly. As is well known in the art, such catalysts are usually applied to the fabric to provide therein about 1 to 10%, e.g., about 5%, catalyst based on the weight of the precondensate fixed in the fabric. Of course, when a certain fabric tends to become tendered or otherwise adversely alfected by a particular catalyst, as happens in some cases when zinc chloride is used, a more harmless catalyst, such as magnesium chloride, is preferably employed.

As previously suggested, a softener such as finely dispersed polyethylene may be included in the catalyst bath as is also otherwise well known. After catalyst impregnation and drying under mild conditions, the fabric is ready for apparel manufacture, e.g., for cutting, sewing, pressing and final dry curing to provide durable press characteristics.

The final cure may be effected in a walk-in air oven at temperatures between about and 180 C., e.g., between and 165 C. For instance, a residence or dwell time of about 5 minutes in an air oven at C. gives satisfactory cure in a typical case though curing times in the range from between about 2 to 10 minutes can commonly be used. Curing may, for instance, also be accomplished in equipment such as a garment press which has been provided with adequate heating and dwell time control means. Optimum cure times of course depend somewhat on the specific kinds and amounts of resin used, the type of fabric and the temperature and heat transfer characteristics of the curing equipment.

It will be understood, of course, that the essential novelty of the present invention lies in the wet fixation or sensitizing step and that after such wet fixation the fabrication of articles from such a treated material is conducted in an otherwise conventional manner.

Fabrics or fiber systems The invention is applicable in the fixation of crosslinking agents or agents which exhibit similar chemical behavior or reactivity, to a wide variety of fibrous materials or systems which contain natural cellulose fibers such as cotton or linen or regenerated cellulose such as viscose or high wet modulus (polynosic) rayon; and in other treatments, e.g., in dyeing, the invention is applicable not only to cellulosic materials, but also to other materials such as wool, silk, poly(vinyl alcohol) and the water swellable nylons. The invention may be applied to fibers, filaments, staple, sliver, tow, yarns and threads but is particularly useful when applied to woven, knitted and non-woven fabrics or webs. It is especially useful in the manufacture of durable shape retentive garments, tufted carpets, molded cotton batting and so forth, but offers important advantages in other treatments of water swellable Webs as well, for instance, in dyeing. The invention is, of course, also applicable to fabric blends, e.g., blends which contain 15% or more of cotton or other cellulosic fiber mixed with polyester, nylon, acrylics or wool fibers.

Specific examples A number of illustrative runs were conducted in accordance with the present invention using 100% cotton twill fabric. This fabric, hereafter sometimes referred to as NCC Twill, had a weight of 7.6 ounces per square yard and a thread count of 116 X 52.

EXAMPLE 1 Samples of the NCC Twill were padded to 80% wet pick-up in baths containing 20% of Aerotex 23 alkylated melamineformaldehyde precondensate and 20% of 9 Permafresh 183 dihydroxydirnethylol ethyleneurea (DHDMEU), the percentage figures referring to resin solids based on weight of bath, 0.1% of Triton X-l surfactant and H'Cl in an amount sufficient to lower the pH of the bath to 2 or 3, as indicated in Table I.

To wet-fix the resins, each wet-padded fabric sample was pinned to a wooden reel and the reel was immersed in a saturated (30%) solution of Na SO at 80 C. After the indicated time, the reel was withdrawn and the fabric sample was washed successively in running water, in 2% aqueous sodium carbonate solution, and finally again in water. The treated fabric was then air dried at about 100 C., conditioned overnight so that it would reach its normal moisture regain (about 7%), and weighed. The add-ons calculated from the conditioned weights beof the resin as exposure to the acid bath is extended beyond the optimum.

TABLE II-A.ADD-0NS or RESIN ON COTTON TWILL TREATED WITH MIXTURE OF POLYMER FORME R P-225" AND CROSS-LINKER 183" BY SALT'SOLUTION WET-FIX- TABLE II-B.PROPERTIES OF TWILL WET-FIXED BY THE SALT-SOLUTION METHOD AND CURED WITH ZINC NITRATE Property retention compared to Wrinkleuntreated fabric, percent Heating Durablerecovery time, Add-0n, press angle Abrasion Tear Breaking Salt solution minutes percent value W+I resistance strength strength Sample:

D2 NazSOi 5 8.3 2.8 281 94 54 59 43..." N82S04 15 11. 4 2.0 267 167 50 64 E-1 Alz(SO4)a 1 9.3 3.3 294 76 48 53 E2... Aiz(S04)a 5 10.8 2. 5 272 88 50 68 E3 A12(SO4)5 15 9. 1 3.0 255 137 51 67 TABLE I.ADD-0NS OF RESIN OBTAINED BY WET- FIXATION IN SATURATED NazSO; AT 80 C.

Add-on o1 resin,

Acidity Heating percent of of salt time, conditioned bath, pH minutes weight EXAMPLE 2 The conditions of Example 1 were followed, except that Aerotex P-225 hexakis (methoxymethyl) melamine was substituted for Aerotex 23 and a 40% A1 (S0- solution replaced the Na S0 solution in some tests. The resin add-ons obtained are shown in Table II-A.

Table II-B shows the properties obtained on samples of these wet-fixed fabrics, after washing, drying, padding to apply thereto 0.5% ZnNO and 1% polyethylene softener, and after drying and dry curing these fabrics.

In the case of Samples D-1, D-2 and D-3, which were wet fixed at the relatively mild pH of 4, the fixation of the resins in the saturated solution of Na SO was found to be relatively slow but the wet-fixed add-on increased substantially as the fixation time was increased from 1 to 15 minutes. In the case of Samples E- l, 13-2 and Er3, which were wet fixed in a strongly acid aluminum sulfate bath, resin fixation occurred much faster and the resin add-on was in excess of 9% on all three samples, even on the one which was heated in the bath for only one minute. The add-on increased only a little as fixation time in this bath was extended from 1 to 5 minutes and then decreased as the time was extended further. The latter effect is probably attributable to progressive hydrolysis All of the cured fabrics had durable-press appearance ratings in the range of 2 to 3.5, and wrinkle-recovery angles (W+F) between 225 and 295; a sample that had been wet-fixed for 1 minute in AI (SO solution exhibited the highest values. This sample also showed the lowest percentage retention of strength and abrasion resistance. The tear strengths of all of the cured fabrics were on the low side, but the breaking strengths were satisfactory and the values for abrasion resistance were farily good, compared to available data on the corresponding properties of similar fabrics prepared by other wet fixation processes.

EXAMPLE 3 The procedure of Example 2 was followed, except that 15% resin based on the weight of the fabric was applied to the cotton twill, a 60% solution of CaCl at pH 1.5 was used for fixation instead of the Na S0 or AI (SO solutions, and the temperature of the salt solution was higher than C. in some treatments. The add-ons obtained are shown in Table III.

As in Table II-A, the data in Table III again show that satisfactory resin add-on is obtained by heating the padded fabric in the acid salt bath for 0.5 to 15 minutes, but that 0.5 to 5 minutes is generally sufiicient and that extended heating may result in a decrease in add-0n. Increasing the fixation bath temperature from 80 C. to C. tends to increase the resin add-on, but increasing the temperature further to C. brings about a substantial reduction in resin add-on. Presumably, this effect is also attributable to the increased rate of hydrolysis caused by such a strongly acidic bath at such high temperatures. Of course, with baths having a higher pH temperatures of 125 C. or even higher may actually be preferred. It will be understood that the bath pH, temperature, fixation time and resin composition are interdependent variables and that it is therefore advisable to establish the optimum combination empirically for each specific case.

EXAMPLE 4 Fabric samples were padded to apply 15% solids on weight of fabric of a 1:1 mixture of polymer former P- 225 and crosslinker 183. Following impregnation, the fabrics were heated in CaCl solutions, under various conditions of pH, time, and temperature. After wet-fixation, the fabrics were cured with Zn(NO as catalyst in a standard manner and laundered once. The properties of these fabrics are given in Table IV.

TABLE III.ADD-ONS OF RESIN ON NCC TWILL TREAlEw WITH POLYMER FORMER P-225 AND CROSS-LINKEDR 183 WITH FIXATION IN 60% CALCIUM CHLORIDEte SOLUTION AT pH 1.

Add-on, percent of conditioned wt. after indicated heating time, minutes Temperature of CaClz soln., C. 0. 5 1 5 No'rE.The fabric was padded to apply 15% resin solids at 60% pick-up.

Table IV shows that most of the fabrics immersed for from 0.5 to 1 minute in the wet fixing bath, and most particularly those treated in the salt bath at a pH of about 2.5, and then finally dry cured in a conventional manner have a combination of physical properties which is indicative of excellent durable press performance.

More particularly, such fabrics have a durable press appearance value of at least 3.0 or preferably at least 3.5, a Wrinkle recovery angle of at least 275, the retention of at least about one-half of the original fabric strength and an abrasion resistance equal to that of the untreated fabric.

EXAMPLE 5 'Fabrics were padded to apply 15% solids on weight of fabric of a 1:1 mixture of a polymer former Aerotex P-225 and a cross-linker Permafresh 183 or, in one experiment, 7.5% solids on weight of the fabric of Aerotex P-225 alone. All of the pad baths were acidified to pH 2 with hydrochloric acid before padding. Following impregnation, the fabrics were heated in 30% Na SO solutions at 100 C. and various conditions of pH and time to Wet-fix the resins in the fabrics. The pH of the wet-fixation bath was adjusted by addition of sulfuric acid. After the wet-fixation, the fabrics were cured with Zn('NO as catalyst and laundered once prior to evaluation.

As may be seen in Table V, the fabrics that were wet fixed by immersion in the salt solution for 0.5 to 1 minute had satisfactory properties. At higher immersion times the wrinkle recovery angle tended to decrease significantly and in the more acid baths it tended to drop below the preferred minimum of 275. Moreover, in the absence of any highly active cross-linker in the pad bath the wet-fixed resin add-on as well as the durable press value of the resulting cured fabric tended to decrease unduly with an increase in exposure to the wet fixation bath, although the efliciency of fixation remained high.

EXAMPLE 6 Wet fixation was attempted by immersing samples of wet, resin-treated fabrics in water containing 1% of sulfuric acid but no salt. Exposure of fabrics to this solution for 1 to 15 minutes at 80 C. were ineffective, in that the treated fabrics had barely measurable add-ons of Wet-fixed resin. This shows that satisfactory wet fixation of a water-soluble agent is impossible in an aqueous medium unless the latter contains an adequate concentration of a salt as a solute.

EXAMPLE 7 For comparison, data are presented in Table VI on twill fabric in which the creaseproofing agents were either wet-fixed by the well-known plastic envelope method prior to a final dry cure in the presence of Zn(NO' catalyst, or applied by the conventional pad-dry cure technique. Comparison of these results with those obtained in Examples 4.and 5 shows that the fabrics which had been wet-fixed in CaCl or Na SO solution for 0.5 to 1 minute had essentially the same properties as the fabrics which were wet-fixed by the plastic envelope method. Of course, wet fixation in a salt solution offers many important processing advantages over the tedious plastic envelope method. The samples prepared by the conventional pad-dry-cure process had a somewhat higher appearance value and Wrinkle recovery angle, but markedly lower strength and abrasion resistance.

TABLE IV.PROPE RTIES OF RESIN-IMP RE GNATED NCC TWILL WET-FIXED BY IMMERSION IN SATURAT- ED CALCIUM CHLORIDE AT VARIOUS TEMPERATURES AND pH VALUES AND CURED WITH ZINC NIT RATE AS CATALYST 1 Wet fixation Property retention compared to Immer- Wrinkleuntreated fabric, percent sion Resin, Etliciency, Durablerecovery Temp., time, percent percent of press degrees Abrasion Tear Breaking pH of salt solution 0 minutes OWF 2 applied resin value W-i-F resistance strength strength 1 The fabric samples were padded to apply 15% OWF of mixed resin ("P-225 and 183). They were cured with zinc nitrate,

laundered, tumble dried, and conditioned before evaluation.

2 On Weight of fabric. 8 Solids applied to fabric after wet-fix/after padding.

TABLE V.PROPERTIES OF RESIN-IMPREGNA'IED NCC TWILL WET-FIXED BY IMMERSION IN SATURATED SODIUM SULFATE SOLUTION AT 100 C. AND WITH VARIOUS VALUES OF pH Resin applied, percent Wet fixation Property retention compared to OWF Wrinkleuntreated fabric, percent Immer- Efiiciency, recovery s1on percent of Durableangle, Aerotex PermapH of salt time, Add-on, applied press degree Abrasion Tear Breaking P-225 fresh 183 solution min. percent resin value W+F resistance 1 strength 3 strength i 0.? g 285 100 66 59 286 100 67 57 7 5 7 5 2 5 5 6.1 34 as 268 200 78 c7 15 6.7 38 3.8 264 200 82 65 0.? g g 289 60 57 56 292 50 55 58 5 7 5 5. 2 35 4 278 100 65 5s 15 5. 4 36 4 278 100 74 53 O. 5 6. 3 71 5 282 100 70 64 15 u 2 1 5.0 67 3. 5 269 150 80 68 5 4. 3 57 3 256 250 87 69 4. 5 60 3 249 300 96 73 l The fabric samples were cured with zinc nitrate, laundered, tumble dried, and conditioned before evaluation.

1 700 cycles. I 2,800 g. 781b.

Although the use of only a few methylol-containing resins has been illustrated, the disclosed invention is deemed to be broadly applicable to polymerizable resins, including flame retardants, as well as to other kinds of agents such as dyes as suggested earlier in this specification. The basic concept of this invention may be used to effect polymerization and graft polymerization in swollen fibers of ethylenically unsaturated, water-soluble monomers such as the various water-soluble acrylic or methacrylic acid salts (e.g., sodium methacrylate), acrylarnide, and so forth. Both acidand base-catalyzed reactions fall within its scope.

EXAMPLE 8 The wet fixation of dyes on cotton fabrics was carried out by the use of a concentrated salt solution in accordance with this invention and, for comparison, by a conventional process which is often used in the industry.

C. in the saturated sodium sulfate solution gave uniformly dyed samples but of a still darker shade.

Still other variations of the disclosed embodiments and concept will occur to persons skilled in the art without departing from the scope and spirit of the present invention or from the scope of the appended claims. It should also be understood, that in the absence of indications to the contrary, all amounts and proportions of materials are expressed on a weight basis throughout this specification and the appended claims.

The subject matter for which exclusive rights are solicited is particularly pointed out and claimed in the appended claims.

I claim:

1. A process for wet fixing a creaseproofing agent in water-swellable cellulosic fibers in a fibrous web which comprises:

applying to said fibrous web at a temperature between TABLE VI.-PROPERTIES OF NCC TWILL TREATED BY PLASTIC ENVELOPE METHOD AND BY PAD-DRY-CURE PROCESS Wrinkle- Property retention compared to recovery untreated fabric, percent Fixation Durablean e,

addon, press degrees Abrasion Tear Breaking Treatment 1 percent value W+F resistance strength strength Plastic envelope method 2 8. 6 3. 5 291 100 54 47 Pad-dry-cure 3 10, 1 4. 0 304 50 39 42 l Wet-fixed samples were cured, then laundered once, tumble dried, and conditioned before evaluation.

2 A 40% solution of a 1:1 mixture of Aerotex P-225 and Permat'resh 183 (solids basis) was applied to the cloth samples, the samples were wet-fixed by heating for 15 minutes at 100 C. in a then washed, recatalyzed, dried and cured.

Mylar plastic envelope, and

B A 15% solution of Permafresh 183 was applied to the samples by padding and the samples were then dried and cured according to the conventional pad-dry-cure technique.

A 3.5 ounce, 80 x 80 cotton print cloth was padded through an aqueous dye bath that contained 5.0 g. of Pontamine Sky Blue 6BX (a direct dye) and 0.1 ml. of wetting agent (Triton X-100) per 100 ml. of solution at 6070 C. for just sufficient time to ensure thorough wetting of the fabric. The padded fabric was then divided into two portions, each of which was passed into a fixing bath without intermediate drying.

In the conventional process, the padded fabric was immersed in an aqueous fixing bath that contained 2 g. of NaCl per 100 ml. of solution at 8S90 C. for 20 minutes, and then rinsed and air dried. Considerable bleeding of dye from the fabric was observed during rinsing, but the fabric was dyed uniformly.

In the process of the invention, the padded fabric was immersed for 1 minute at 100 C. in a bath that was saturated with sodium sulfate and adjusted to a pH of 4.5 with sulfuric acid, and the treated fabric was rinsed and air dried as before. Much less bleeding of dye from the fabric occurred during rinsing, and the fabric was dyed uniformly but of a darker shade.

A test run similar to the last was carried out but the pH of the bath was adjusted to 2.5. Again, 1 minute at 100 about 0 C. and about 40 C. a first aqueous liquid at a pH between about 1 and 7 and containing between about 5% and 25% of at least one watersoluble, hardenable creaseproofing agent possessing reactive N-methylol groups to deposit the creaseproofing agent within wet and swollen cellulosic fibers in said web, the creaseproofing agent being deposited in said web in an amount sufiicient to deposit in said web at least about 3% of creaseproofing agent based on dry web weight,

immersing said web having said aqueous liquid applied thereto in a second aqueous liquid at a pH between about 1 and about 7 and which is not detrimental to said web or to said creaseproofing agent, said second liquid being an aqueous solution which contains a water-soluble stable salt of a strong acid which does not decompose in water and is dissolved therein in a salt concentration which is suificient to prevent any substantial migration of creaseproofing agent out of said web while avoiding formation of solid deposits thereon, the second liquid maintained at a treating temperature above about 70 C. and below the boiling point of said first aqueous liquid,

maintaining said web in said second liquid containing said stable salt at said salt concentration for a period sufiicent to wet fix the creaseproofing agent within cellulosic fibers in said web while avoiding efiective creaseproofing and the formation of solid deposits or precipitates on said web,

removing said web from said second liquid,

removing residual water soluble solids from said web,

and drying said web under mild conditions in preparation for the manufacture of a durable press article therefrom.

2. A process according to claim 1 wherein said fibrous web contains at least 20% cellulosic fibers, the pH of the first aqueous liquid is adjusted to between about 1 and 3,

and the creaseproofing agent comprises a formaldehyde/ melamine precondensate characterized by a formaldehyde/melamine ratio of between about 3:1 and 6:1 and wherein said second liquid is a solution containing sodium sulfate at a concentration between 50% and 100% of saturation.

3. A process according to claim 1 wherein said second liquid is an aqueous solution containing dissolved therein between 15 and 75% of a water-soluble salt of a strong base and a strong acid.

4. A process according to claim 1 wherein the stable salt is at least one mineral acid salt of a member selected from the group consisting of an alkali or alkaline earth metal, zinc, magnesium, and aluminum.

5. A process for wet fixes a creaseproofing agent in water swellable cellulosic fibers in a fibrous web, which process comprises:

applying to said fibrous web at a temperature between about C. and about 40 C. a first aqueous liquid at a pH between about 1 and 7 and between about to 25% of at least one water soluble, hardenable creaseproofing agent possessing reactive N-methylolgroups to deposit the creaseproofing agent within wet and swollen cellulosic fibers in said web, the creaseproofing agent being deposited in said web in an amount of at least about 3% of creaseproofing agent based on dry web weight,

immersing said web having said aqueous liquid applied thereto in a second aqueous liquid containing between 15% and 75 of a slufate salt of at least one member selected from the group consisting of an alkali or alkaline earth metal, magnesium, zinc, and aluminum, dissolved in an aqueous medium and having a pH between about 2 and about 4, the sulfate salt being stable and not decomposing in water and dissolved in the liquid in a concentration sufficient to prevent any substantial migration of creaseproofing agent out of said web without forming solid deposits thereon, the second liquid being maintained at a treating temperature above about C. and below the boiling point of said first aqueous liquid,

maintaining said web in said second liquid for a period sufiicient to insolubilize by polymerization the creaseproofing agent Within the wet and swollen cellulosic fibers in said web,

removing said web from said second liquid,

neutralizing the acidity in the web,

washing residual water soluble solids from said web,

drying said web under mild conditions and subsequent to removing the web from the second liquid impregnating the web with a latent curing catalyst in preparation for manufacture of a durable press garment therefrom, the latent curing catalyst comprising a salt selected from the group consisting of zinc nitrate, magnesium chloride, ammonium chloride and zinc chloride.

6. A process according to claim 5 wherein the pH of the first aqueous liquid is adjusted to between about 1 and 3, and the creaseproofing agent comprises a formaldehyde/ melamine precondensate characterized by a formaldehyde/melamine ratio of between about 3:1 and 6:1.

7. A process according to claim 5 wherein said second liquid is a solution containing sodium sulfate at a concentration in the liquid between about 20% and 30%.

8. A process according to claim 5 wherein said second aqueous liquid is maintained at a temperature between about and C. and said web containing said solution of creaseproofing agent is immersed in said second liquid for a period ranging from about 0.5 to 5 minutes.

9. Process according to claim 8 wherein said second liquid is a solution containing sodium sulfate at a concentration between 50% and 100% of saturation.

References Cited UNITED STATES PATENTS 2,973,285 2/1961 Berke et al. 1l762.2 2,493,381 l/l950 Balassa 1l762.2 3,420,699 1/1969 Mard et al. 1l762.2 3,138,802 6/ 1964 Gctchell 11762.2 3,310,419 3/ 1967 Wagner ll7-62.2 3,167,446 1/1965 Nijs 1l762.2 2,962,392 11/1960 Haycock et al. 117-161 LN 3,524,763 8/1970 Taravella ct al. 117-161 LN WILLIAM D. MARTIN, Primary Examiner M. SOFOCLEOUS, Assistant Examiner US. Cl. X.R.

117139.4, A, 143 A, L, 161 LN 

